Eye Snake

Soundbyte

If you ever thought you couldn�t control things with your eyes, think again � here�s the game Snake that allows 4 modes of multi-level game play with buttons or with your eyes, using electro-ocular potential.

Project Summary

While brainstorming for a 476 final project that would be biomedical engineering-related, we stumbled upon the idea of utilizing electrodes hooked up to a human sensory system. Through Google, we found that Boston College had invested on a new technology, EaglesEyes Project, where people with disabilities to be able to utilize their eyes or head to control the computer. Game lovers ourselves — it is through this project that we were inspired to come up with our current 476 final project. Effectively, this game would allow even those with disabilities to successfully play video games. Because of limited budget, test subjects, costs, and other resources, we proposed and successfully constructed a simulated version of the game �Snake�, utilizing an electroculogram that would sense a generated potential from eye movements through electrodes.

Many thanks to Luana Shen, who spent countless unmoving, evening hours in lab! Without her patience and our other test subjects, this project would’ve been almost impossible.

Note: THIS IS A STUDENT PROJECT, NOT A MEDICAL DEVICE! Before trying to wire yourself up to a TV, read carefully.

Eye Snake – High Level Design

Project Rationale

In 1848, Emil du Bois-Reymond observed that the cornea of the eye is electrically positive relative to the back of the eye. It is as if the eye were acting as a single dipole oriented from the retina to the cornea. These corneoretinal potentials are well in the range of 0.4- 1.0 mV. Therefore as the eye moves, this moving and rotating dipole source generates signals that can correspond to eye movements. This forms the basis of the electro-oculogram (EOG). Typical signal magnitudes range from 5-20 �V per degree. The electro-ocular potentials were interfaced with the Snake game to test the user�s ability to play the game by moving their eyes left, right, up and down. Because it is difficult to view the screen if the user�s eyes are held in the position of �left,� the direction of the snake�s movement will be triggered when the user moves his/her eyes in that direction, whereupon the snake will continue to travel in that direction until the user�s eyes indicates a change in direction. Also, while it would be ideal for the user�s eyes not to swing from corner to corner, we�re not able to ensure that for each test subject and between each individual subject that they would be move their eyes to an angle of thirty degrees consistently. Therefore, left corresponds to rolling your eyes all the way to the left, and up corresponds to looking up at the ceiling.

The figure above shows the measurement of horizontal eye movements by placing a pair of electrodes outside of the left and right eye where the outer canthi are. At rest, the electrodes will be the same potential and thus, no voltage is recorded. The rotation of the eye to the right causes the difference of the potential to be the positive in the direction of movement relative to the second electrode. This same concept applies to the measurement of vertical eye movements as well.